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Rad vent cycling rapidly can this be normal? Adventures with different vents

I put one of the more expensive brands of rad vents on a particular rad, expanding liquid type vent, less than one season old. It will rapidly cycle every four seconds or so, pffffft TING!, pffffft TING! over and over. It's in a bedroom, so this is a little annoying. What is up with this. I seem to recall it also behaved this way on a different rad in the past, before I banished it to my 'spares' pile.

The prior vent I had on this rad was an expensive bi-metal type. After less than two seasons, the bi-metal vent hissed for minutes on end, like maybe it wasn't closing. Hard to tell. I soaked it in vinegar for a few hours. The vinegar turned blue. When I threw it back on the rad, no change, behaved the same way.

The new vent I currently have on this rad is a different expensive brand of expanding liquid type. This is a real beauty. Despite a standard size hole, man, this radiator is hot hot hot now. Why? In any event, although it is a little quieter, I still hear a a surprising amount of not-as-loud air/damp air/steam/who knows movement out of the rad for minutes on end. The breathing in seems to be less noticeable.

On a different bedroom rad, same expensive bi-metal brand as the other I tried to clean, fast variant (occupant had complained of cold), it started continuously rattling after less than two seasons. So I took that one off, reached into my 'spares' pile, and threw on what a lot of people say is a cheaply constructed bi-metal. This one is silent and the radiator heats fine, no complaints. Go figure. I have this same less-well-regarded bi-metal brand on a different radiator for two seasons now, and that one, too, is completely silent, and the radiator heats fine. Go figure.

I think I have tried every vent brand now. It seems more art than science. It also seems like quality control may be a bit uneven.


  • neilc
    neilc Member Posts: 2,667
    let's go back to the basement,
    what do you have for mains and main vents?
    what do you see for boiler pressure when the rads upstairs are making all that music?
    known to beat dead horses
  • ethicalpaul
    ethicalpaul Member Posts: 5,605
    Name and un-shame the inexpensive bi-metallic workhorse! (I'm betting MoM)
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el